1. Field of the Invention
This invention relates to waste disposal systems and, in particular, to a commercial aircraft galley waste disposal system.
2. Description of the Prior Art
In commercial aviation, it is necessary to dispose of unwanted fluids and solids such as human waste and food waste. Disposal of human waste is accomplished with the use of toilet systems such as conventional vacuum toilet systems. Since about the early 1980's, it has become common to use vacuum toilet systems in large commercial aircraft. These vacuum waste systems typically include a toilet bowl for collecting waste, a waste holding tank, a vacuum pump, and a valve system for placing the toilet bowl in communication with the waste holding tank. A rinse valve controls the introduction of rinse water into the toilet. The system is typically controlled by an electronic controller.
The problem of disposal of food waste has not yet been fully addressed. During in flight operation of commercial aircraft, a large quantity of food and beverage leftovers can accumulate on an airplane, the volume depending on the number of the passengers and the duration of the flight. This leftover waste can come in the form of solids, liquids, and/or a mixture of the two, called "slurry." Thus, the handling of this waste is an issue, particularly on longer flights having many passengers. During such flights, holding the waste in the aircraft galley (food preparation area) on the trays and in the carts in which the food and beverages are served for the duration of the flights is: 1) impractical because of the relatively large quantity of food stored and served; 2) unsanitary; and 3) can be unsightly.
Currently, most commercial aircraft are equipped with galley sinks. However, these sinks are intended for the disposal of fluid waste only as they are connected to small diameter drain lines, ranging from about one half to one inch in diameter, and terminating at the aircraft drain mast for exhaustion to the atmosphere. Unfortunately, such sink systems are unable to dispose of slurry and solid food waste products.
In response to this problem, flight attendants have often been instructed to dispose of solid and slurry food wastes into the toilets which are located near the galleys. Conventional aircraft vacuum toilets are effective for disposing of such food waste products for a number of reasons. First, they are connected through much larger lines, typically two inches in diameter, to waste holding tanks. Further, conventional aircraft vacuum toilet systems transfer waste from the toilet bowl to the waste holding tanks via a differential pressure action, thereby ensuring immediate and complete evacuation. In particular, the air pressure in the toilet bowl is at cabin pressure (which is pressurized for the safety and comfort of those on board), while the drain line is maintained at a much lower air pressure from a source of vacuum. This source is typically either a vacuum pump or the atmospheric pressure outside of the airplane, which is very low at cruising altitudes of thousands of feet above sea level. This differential reaches approximately 8.5 p.s.i. at an altitude of about 35,000 feet. Thus, when the flush valve separating the two atmospheres is opened, a strong vacuum action results and powerfully draws the contents of the toilet bowl into the waste holding tanks.
While disposing food waste in aircraft toilets is effective for its removal from the cabin, several problems and disadvantages have been identified. First, it can be quite unsanitary for a flight attendant to enter into a lavatory to dump food waste into a toilet bowl while working with food in the galley. For example, given the time demands on flight attendants, there is a possibility, and perhaps even a likelihood, that they will fail to wash their hands each time they exit the lavatory. Second, requiring attendants to dispose of food wastes in toilets is both inconvenient and inefficient. The process requires the attendant to carry the container holding the waste from the galley to the lavatory, open the door, bend down to the level of the toilet bowl and pour the waste into the bowl, taking care that it does not spill anywhere but in the bowl. This may have to be repeated several times until all or enough of the food waste is flushed down the toilet.
Further, using a toilet bowl requires, of course, that one be available. However, availability of the lavatories is subject to their occupancy by the passengers. It would be inefficient for an attendant attempting to complete the task of cleaning up after a meal to have to wait until a toilet became available. Additionally, requiring flight attendants to use toilets for the disposal of food waste appears unprofessional and can be distasteful to the flying public.
One approach to the general problem of food waste disposal during in flight operation of commercial aircraft, which has come to the inventor's attention, has been a proposed design for a galley sink system based closely upon existing aircraft vacuum toilet designs. Thus, such a sink system would include a drain line having a much larger diameter than conventional galley sinks and would operate on the same differential pressure, or vacuum, theory used by conventional vacuum toilet designs.
While generally effective for disposing of solid, liquid and slurry food wastes, implementing one of the conventional vacuum toilet designs into a galley sink system is unsatisfactory for numerous reasons. First, these designs do not account for the potential for clogged drain lines. In particular, if and when the drain line of a conventional vacuum toilet becomes clogged, flush cycles may continue to operate and rinse water may continue to be introduced into the bowl despite the lack of pressure differential between each side of the flush valve (i.e. between the bowl and the drain line). Thus, the system is enabled until the stoppage is identified by an individual and the problem is corrected. Under this condition, the toilet bowl itself could even eventually begin to fill with a mixture of rinse water and black, or human waste, water. However, due to sanitation concerns and health and safety regulations, this situation would be unacceptable in a galley sink environment, where the sink bowl may not become contaminated with either used sink water, called grey water, rising from the clogged sink drain line, or black water rising from the aircraft's main drain line.
A second problem concerns the potential for large objects being dropped or flushed into the drain line. Certain objects often found in a galley, including chopsticks, cutlery, and large bones, while too large to be disposed of by a galley sink system, could inadvertently enter into the sink bowl, and, because of their elongate and relatively narrow shapes, pass the sink bowl's waste disposal outlet, enter into the drain line and become lodged therein. Other objects, such as solid food waste that would normally pass through the system could then become engaged with the lodged object, eventually leading to a clogged condition. Even worse, the large object could find its way into the flush valve assembly and cause the flush valve to malfunction or break. Thus, such an obstructed object must be promptly removed from the drain line. However, with conventional drain line designs, its removal would be quite burdensome, requiring disassembly of the galley sink drain line. Further, the lodged object may not be identified until only after one of the aforementioned, or other, resultant problems arise. Thus, a need exists for a galley sink system that prevents such an object from becoming lodged in the drain line while permitting other food wastes to enter into the line for disposal.
Another problem with the earlier galley sink design relates to noise. A loud flushing sound is created when the flush valve opens and the differential pressure across it forcefully draws the waste down the drain. The lid, or shroud, of the earlier galley sink design, based closely on conventional toilet shrouds, somewhat helps reduce the noise output, but not to a sufficient degree. This noise level has generally not been objectionable for aircraft toilets because they are located within lavatories whose doors are typically closed when flushing occurs. Therefore, the noise is relatively isolated from the passengers during flushing. Also, the toilet bowl height, typically at sixteen inches, is almost three feet away from the typical passenger's ears, thus reducing the impact of high sound level. However, this same level of noise would be unacceptable in the galley of the aircraft. The galley is typically in an open area and close to at least some passengers who could hear the flushing noise even with a conventional toilet-type lid covering the sink. Further, the sink in a galley is mounted much higher off of the floor, typically 44 inches high, and is closer to the ears of the operators than is the case with toilets. Thus, a definite need exists for a galley waste disposal that is quiet enough in operation not to disturb passengers and attendants.
A further problem of the earlier galley sink design and conventional toilet designs relates to the potential for overflow of waste onto the floor or into the cabinet which may house the sink. Since the top of the sink must be covered for the sake of noise reduction, in order to allow cabin pressure air to enter the bowl to create the differential pressure needed for vacuum flushing, an overlapping shroud design has been suggested. In this sink design, which is similar to conventional toilet designs, a shroud covers over the sink but maintains an opening around the perimeter, or mouth, of the bowl to allow air to enter. One problem that can arise is that when the sink bowl starts to fill up with waste to be disposed, excess fluid could overflow under the shroud and into the cabinet without the attendant recognizing the overfill condition. Such fluid waste entrapped in the cabinet could cause erosion and odor problems and would likely require frequent maintenance. Thus, a need exists for a galley sink system that eliminates the potential for overflow spillage, particularly in the cabinet which houses it, if there is one.
U.S. Pat. No. 5,165,457, issued to Olin et al., describes a vacuum toilet sewer arrangement for a toilet bowl including an air tight lid made of relatively sound-proof material to the reduce the noise associated with vacuum flushing action. Enablement of a function impulse, such as a user-operated push button, can be made dependant on the closing of the lid. Further, an air tube is connected to the toilet bowl in order to provide the ambient air necessary for efficient vacuum flushing. While incorporating these toilet system features into a galley sink disposal system would address some of the aforementioned problems, the potential concern that is unique to a vacuum galley sink system, namely the clogged drain situation, is not addressed by this patent.
In sum, there exists a definite need for a galley waste disposal system that prevents a backup into the sink bowl upon a clogged drain condition, that is quiet in operation, that cannot overflow into the cabinet in which it is housed, and that does not permit elongate objects that could get stuck in the drain line from entering the line.